1. Field of the Invention
This invention relates to a preheating device for a fluid/fluid heat exchanger of an aircraft, more particularly for a fuel/oil exchanger of an aircraft power plant.
An aircraft comprises an airframe and at least one propulsion system. According to a widely used embodiment, a propulsion system is suspended under a wing by means of a mast. More generally, the propulsion system is connected to the airframe by means of a mast.
2. Description of the Related Art
A propulsion system comprises a gas turbine engine that is equipped with an engine cooling circuit, in which a coolant (or cool fluid), in particular oil, circulates.
The gas turbine engine is supplied with fuel by means of a fuel circuit that extends from a reservoir that is placed at the airframe.
In some cases, it is possible to use several cooling sources for cooling the oil of the gas turbine engine, and in particular a fuel/oil exchanger at the level of the engine cooling circuit, and to use the fuel as coolant so as to cool the oil of the gas turbine engine.
This arrangement is described in particular in the patent application FR-2,936,224, which proposes a process that uses the fuel as a coolant between the airframe and the propulsion system.
According to an embodiment that is illustrated in FIG. 1, an exchanger comprises at least one chamber 10 in which the oil circulates and a number of pipes 12 in which the fuel circulates and which pass through said chamber 10. In this case, the inside surface of the pipes 12 is in contact with the fuel whereas the outside surface of said pipes is in contact with the oil. These pipes are essentially rectilinear and have a constant diameter D. Upstream, this exchanger also comprises a fuel supply pipe 14 that can be connected to a duct, not shown.
The chamber 10 is separated from the pipe by a plate 16 that comprises a number of openings 18 with a cross-section that is constant and equal to D, and said openings each work with a pipe 12.
Under certain flight conditions, solid elements may appear in the form of ice crystals in the fuel that may have large dimensions preventing them from entering the pipes 12 via the openings 18. Thus, the surface of the plate 16 that is oriented toward the fuel supply pipe 14 is potentially a zone in which ice crystals can accumulate, and the ice crystals run the risk of limiting the flow of fuel in the direction of the power plant.
The document FR-2,318,314 provides a second exchanger for preheating the fuel so as to limit the accumulation of ice crystals in the first exchanger. However, the risks of ice crystals accumulating are transferred to the level of the second exchanger.